The swimmer Ian Thorpe, one of the most popular and successful sportsmen in Australian history, has spent much of his life battling crippling depression.

In a book about to be published, Thorpe revealed that his illness was so severe he considered suicide and planned specific places and ways to kill himself. He also confessed to drinking huge quantities of alcohol to rid his head of terrible thoughts and to manage his moods.

''It was the only way I could get to sleep. It didn't happen every night but there were numerous occasions, particularly between 2002 and 2004 as I trained to defend my Olympic titles in Athens, that I abused myself this way - always alone and in a mist of disgrace,'' he said.

Thorpe also met persistent questions about his sexuality head on: ''For the record, I am not gay and all my sexual experiences have been straight. I'm attracted to women, I love children and aspire to have a family one day ...

"I know what it's like to grow up and be told what your sexuality is, then realising that's it's not the full reality. I was accused of being gay before I knew who I was.''

In his latest book, This Is Me: The Autobiography, written with Robert Wainwright, Thorpe said he had never spoken about the complications of his life and his parents were unaware he had suffered crippling depression.

''I know the illness can't be blamed or used as an excuse for poor results. I was able to swim some of my best times through some of the worst periods,'' he said. ''And it also wasn't a reaction to the high life of red carpets and speeches, and neither can I blame the media intrusion - although it certainly hasn't helped and might explain my reticence to discuss my private life. It's a terribly dark place in which to hide.''

Thorpe, 30 today, said he wanted to be the perfect child and kept what he felt was a ''character flaw'' secret from his parents: ''But now I realise it's time to be open. I need to talk to them about it ... I know how Mum will react. She'll cry and ask me why I didn't tell her and then she'll tell me how proud she is that I've finally talked about it. Dad is different. I'm not sure how he'll react. I know it'll take time for him to come to terms with it and how it fits in with his religious beliefs.

I hope it does, because family means a lot to me.''

Thorpe said he thought the incidence of depression was quite high among elite athletes. His blackest periods would often last a month, which was when he contemplated suicide.

''I even considered specific places or a specific way to kill myself - but then always baulked, realising how ridiculous it was. Could I have killed myself? Looking back, I don't think so but there were days in my life that even now make me shudder.''

In an article accompanying an extract from his book, Thorpe said he was confident he would soon find a partner. ''In fact, I have someone in mind who I got introduced to by a friend,'' he told the journalist Jane Wheatley. Is she Australian? He won't say. How long has he known her? A few months.